The interconnection of individual circuit components and printed wiring boards, for example, has until recently been accomplished by the well-known method of soldering the component leads to the board wiring. Although effective electrical connections were thus achieved, the soldering operations were time consuming and, further, created connections which were more or less permanent. Replacement of a defective component, for example, necessitated the unsoldering of the defective component leads and the resoldering of the replacement leads thus adding to the cost of circuit maintenance and repair. This problem has been aggravated with the advent of large-scale integrated circuit packs, such as dual-inline packs, for example, having dual groups of many terminals. To meet the problem and obviate the necessity of soldering large numbers of terminals which are usually closely spaced and frequently small, socket connectors have been provided. Such connectors have contact receptacles into which the circuit pack terminals may be inserted, the connector contacts then being permanently soldered to the circuit wiring board. Although the socket connectors offer the obvious advantage of plug-in connection of the circuit packs and thereby facilitate component replacement, the connectors in turn present other problems.
The receptacle contacts of the socket connector generally comprise deflectable free cantilever beam springs which are urged against the circuit pack terminals by spring action after insertion of the terminals in the connector receptacles. The insertion of the terminals is accomplished against the spring action, which action must be sufficient to ensure positive electrical contact. When many circuit pack terminals are involved, which is typically the case, considerable force may be required to insert the many terminals in the corresponding receptacles of the connector. Since the terminals are small and fragile, the insertion force required leaves the terminals vulnerable to bending, misalignment, and other damage to the contact surfaces. The risk of damage, of course, is present on each replacement occasion and the exercise of considerable care has been required to ensure proper seating of the circuit pack terminals.
The foregoing insertion problem has led to the development of so-called zero insertion force connectors. In these connectors, the electrical contact forces on the circuit pack terminals are not fully applied until the terminals are completely or nearly completely inserted in their receptacles. Such a zero or low insertion force socket connector is disclosed, for example, in U.S. Pat. No. 3,883,207, of T. K. Tomkiewicz, issued May 13, 1975. Another prior art connector offering a low insertion force and embodying a unitary molded construction is disclosed in U.S. Pat. No. 3,820,054 of A. B. Clewes et al., issued June 25, 1974. Generally, zero or low insertion force connectors as typified by the examples cited have been more expensive than their conventional counterparts and have increased the cost of circuit pack mountings. A zero insertion force connector has generally been more complex and made up of a larger number of piece parts. As a result, more time was required for their fabrication. Also because of their complexity, zero insertion force connectors have been bulkier, thereby requiring a larger share of printed wiring board area.